A fluid machine in which a plurality of rotating mechanisms are accommodated in a closed casing and the rotating shafts of the rotating mechanisms are coupled linearly to each other has been known, as disclosed on pp. 43-45 of “Strategic Development of Technology for Efficient Energy Utilization—Development of Two Phase Flow Expander/Compressor for a CO2 Air Conditioner,” a report issued in March 2003 by the New Energy and Industrial Technology Development Organization.
FIG. 27 is a view schematically illustrating the fluid machine disclosed in the just-mentioned document. As illustrated in FIG. 27, this fluid machine includes a vertically oblong closed casing 101 as well as a compression mechanism 102, a motor 103, and an expansion mechanism 104, which are accommodated in the closed casing 101. A recessed portion 105a having a regular hexagonal shape in cross section is formed in the upper end of a rotating shaft 105 of the compression mechanism 102. On the other hand, a protruding portion 106a having a regular hexagonal shape in cross section is formed at the lower end of a rotating shaft 106 of the expansion mechanism 104. By engagement of the protruding portion 106a and the recessed portion 105a with each other, the rotating shaft 105 and the rotating shaft 106 are coupled to each other. The recessed portion 105a and the protruding portion 106a together form a coupling part 107 for coupling the rotating shafts 105 and 106.
The compression mechanism 102 and the expansion mechanism 104 need to be supplied with lubricating oil. For this reason, an oil reservoir 112 for holding lubricating oil is provided in a bottom portion of the closed casing 101. An oil pump 115 is attached to a lower portion of the rotating shaft 105, and an oil supply passage 113 is formed inside the rotating shafts 105 and 106. With this configuration, the lubricating oil pumped up by the oil pump 115 is supplied through the oil supply passage 113 to sliding parts of the compression mechanism 102 and the expansion mechanism 104.
Reference numeral 108 denotes an intake pipe for taking in the fluid before compression, reference numeral 109 denotes a discharge pipe for discharging the fluid after compression, reference numeral 110 denotes an intake pipe for taking in the fluid before expansion, and reference numeral 111 denotes discharge pipe for discharging the fluid after expansion.
A similar fluid machine also is disclosed in JP 9-126171 A.